How do I schedule different Leads to send emails on different date ?
When you want to schedule emails to go on pre-determined date for individual leads so that all leads won't be scheduled on single day.
How to stop repeat WARM notification for the same lead ?
Yes you can stop repeat WARM notification for the same lead and same sequence. This is configurable at Assistant->Notifications->Warm Lead Notification.
This stops repeat WARM Lead notification for 180 days. If the same lead becomes WARM again after 180 then you will receive the WARM notification.